Blading of an axial fortative compressor



Jan. 31, 1961 G. B. SOMMARIVA 2,959,909

BLADING OF AN AXIAL ROTATIVE COMPRESSOR Filed Aug. 13. 1957 Multi-stage axial flow compressors of known types are usually provided with blades (stationary and rotating) having aerodynamic shapes. In said types, the fluid passing between two blades of the rotor is only turned through a pattern to cooperate with the blades of the successive stationary rows of blades and thus during the passage between the rotor blades there is no pressure increase due to the blade shape. The same disadvantage, likewise, takes place when the fluid passes between the stator blades. Consequently, a relatively large number of rotor stator couples or stages is needed for obtaining a certain pressure increase of the fluid to be compressed.

The present invention removes the afore-said disadvantage.

The blades according to the invention are characterized by the fact that the flow paths between two adjacent rotor blades and between two adjacent stator blades are shaped as a diffuser, so that, during the passage of the fluid through said flow paths or diifusors the kinetic energy of the fluid changes into pressure energy.

Consequently the desired compression is achieved through a much lower number of rotor/stator couples or stages compared with the known devices.

The blading is characterized by provision of blades in advance of the first row of blades on the rotor suitable to convey, in the desired direction, the fluid into the diffusers of the first row of rotor blades.

A preferred embodiment of the object of this invention is shown, by only way of example, in the annexed drawings:

Fig. 1 is a partial axial section of a multi-stage axial flow compressor.

Fig. 2 shows, in an enlarged scale, the developed sections of the blades of a row on the rotor and of a successive stator blade row.

Referring to Fig. 1: 1 is the compressor axis, 2 is the rotor body, 3 is the stator body, 4 is a stationary row of directing blades giving the air the direction corresponding to c In Fig. 2: 5 and 6 are two successive blades of the rotor, while 7 and 8 are two successive blades of the stator.

The blades 5, 6 of the rotor are disposed in one sense relative to the longitudinal axis of the machine and the blades 7, 8 of the stator are disposed in an opposite sense relative to the longitudinal axis to jointly define between adjacent or successive blades of a given row of blades an optimum angle of entry for the fluid as it passes between the successive rows of blades upon being turned in a manner hereinafter explained. Each of the blades has the same geometrical cross-section. Each blade has an inlet portion 11 having a much greater thickness or cross-section than a discharge portion 12.

The inlet portion is provided with an arcuate leading edge 13 smoothly merging with an arcuate side surface 14 which merges with a substantially flat surface 16 of the discharge portion which is substantially parallel to the longitudinal axis of the rotor or normal to a transverse plane between successive rows and at right angles 2,959,909 Patented Jan. 31, 1961 to the axis of the rotor thereby forming one side of the blade. The opposite side of the blade has a substantially fiat surface 17 making an angle with the longitudinal axis of the rotor. This flat surface 17 extends substantially the full length of the inlet portion and merges with the arcuate inlet edge surface and with the concave surface 18 of the discharge portion which, however, converges substantially along a straight line or path toward the opposite side surface 16 of the discharge portion to form a discharge end 19 which is relatively narrow with respect to the leading end or edge of the blade.

Two successive or adjacent blades in a given row jointly define a diifuser in which a constriction is defined between the leading edge, as for example a leading edge 20, of one of the blades and the next adjacent convex surface of the inlet portion of the adjacent blade. These diffusers function as later explained.

The rotor rotates with a peripheral speed u. The suction action exerted by the compressor imparts to the air the direction and speed c which combining with the speed u results in a resulting direction and speed w which according to the invention is parallel with the tangent ab to an inlet portion of the rotor blades starting from a narrower zone or throat having a width between the blade inlet portions at the inlet end of the diffuser formed between the blades. The distance between the adjacent blade side surfaces increases so that at the outlet it results in a zone having a width l which is larger than the width 1 It follows that the fluid kinetic energy passing through the zone corresponding to the distance or width 1 turns partially into pressure energy. The outlet velocity W2 of the fluid from the conduit between the two rotor blades is lower than the said W1, and has a direction that corresponds with the tangent cd to the outline of the rotor blades in correspondence with the outlet of said diffuser. The same eflect also takes place in the passage of the fluid along the stationary diffuser formed by the two stator blades. The outlet speed W2 of the air from the diffuser between the two rotor blades combines with the peripheral velocity u of the rotor and thus results in a resulting velocity which, similarly to what before was seen about the rotor, is parallel with the tangent ef of the cross section of the stator blades, in correspondence with the reduced zone or throat having a width 1 of the diffuser between the inlet portions of two stator blades. Likewise the fluid passing from the zone having a width 1 to the zone of larger width 1 of the diffuser between two stator blades, is turned through a pattern such that it has a direction of emergence corresponding to 0 to cooperate with the successive rotor.

Further, said passage, considering the variation of the conduit diffuser width from the zone corresponding to 1 to the zone corresponding to 1 results in a further transformation of kinetic energy into pressure energy, and the outlet speed of the fluid from the zone corresponding to 1 will be lower than that 0 The above efiect reoccurs for every successive rotor/stator couple or stage.

Although for describing purposes the present invention has been specificated and shown on the ground of what was before stated, many variations and additions may be brought in embodying the invention, every one however based on the main ideas of the invention, as resumed in the following claim:

What I claim is:

In a machine of the multi-stage axial flow type for converting kinetic energy of a gaseous fluid into pressure rise and having a stator, a driven rotor and a longitudinal axis, a plurality of successive compressor stages comprising alternately arranged rows of angularly spaced radially extending blades on the rotor and the stator each having geometrically alike cross-sections and the space be: tween successive blades being equal in each row of blades, each of the blades having a thick-sectioned inlet portion at an angle relative to said longitudinal axis and. a trailing discharge portion with said. inlet portion substantially thicker in cross-section than said discharge portion with next adjacent blades of respective rows jointlydefining a respective diffuser between them, the blades in the rows on the rotor being disposed in one sense relative to the longitudinal axis of the machine and the blades on the stator being disposed in an opposite sense relative to the longitudinal axis to define a predetermined optimum angle of entry in the successive rows, each blade having a convex leading edge and having oppositely disposed radially extending side surfaces, one of said sides having a convex surface along the inlet portion of theblade smoothly merging with the convex leading edge and smoothly merging with a flat surface of the discharge portion substantially normal to a plane at right angles to the longitudinal axis of the rotor, the opposite side having a surface at an angle relative to said longitudinal axis and substantially fiat along substantially a major part of the inlet portion smoothly merging with the arcuate leading edge and merging smoothly with a concave surface of the discharge portion converging substantially along a straight path toward said surface normal to said plane to define a substantially narrow discharge end, said inlet portion forming a major sectional portion of the blade and the discharge portion being longer than the inlet portion, said leading edge of one of said two adjacent blades in a row and said convex surface of the inlet portion of the other blade jointly defining a throat in the respective diffuser defined between said two adjacent blades, and the concave surface of each of the discharge portions of the individual blades being so curved as to turn in operation the gaseous fluid within the respective diffusers in a direction parallel to a tangent to the straight surface of the inlet portion of the blades of the next successive row of blades so that the gaseous fluid passes through the diffusers through a pattern of turning in which maximum pressure rise is effected in each stage and the gaseous fluid enters the space between adjacent blades of the successive rows of blades in a direction parallel to a tangent to the straight surface of the inlet portion of the blades.

References Cited in the file of this patent UNITED STATES PATENTS 2,406,126 Zweifel Aug. 20, 1946 2,426,270 Howell Aug. 26, 1947 2,446,552 Redding Aug. 10, 1948 2,605,956 Gardiner Aug. 5, 1952 2,652,227 Boestad et al Sept. 15, 1953 2,718,349 Wilde Sept. 20, 1955 2,746,672 Doll eta1 May 22, 1956 

